1. Field of the Invention
The field of technology of this invention is enclosures for retaining integrated circuit cards and related components and peripherals and, more specifically, card guides integrally incorporated into card cages and a method of manufacturing card guides and other multiple level devices in a single step operation using a single tool.
2. Description of the Related Art
Card cages may be used to support one or more printed circuit boards (PCB's) on elements generally referred to as card guides. In addition to supporting the PCB's, these card guides provide a path or track which serves to both permit the PCB to slide into and out of the card cage and to retain the PCB in a selected location in the card cage. Card guides may incorporate other features such as clamping mechanisms, electrical grounding, electrical isolation, heat sinking and shock absorption.
Printed circuit boards include electrical components attached to one or both sides thereof. Any given PCB can differ in thickness, width and length from another PCB, depending on its function, and manufacturer, and as defined by the components secured upon that board. A PCB can include multiple circuit boards which are secured adjacent to or in contact with each other. These boards typically have a base, main or primary board (lower board) and one or more secondary boards. These secondary boards (upper boards) are commonly referred to as piggyback or daughter boards. The piggyback boards may be wider or narrower than the primary board to which they are attached.
Card cages, referred to also as card files, are used to hold PCBs in an orderly and fixed position. The card guides, in turn, establish the distance or spacing between each PCB or multiple board configuration. Some industries have established standards for the PCB spacing, to tailor the design to match the specific design requirement for the application. In fact, the spacing need not be uniform from board to board, nor does a company always use standards, feeling that they must customize the design of the board spacing.
Interconnecting the PCBs is still another design requirement. At least two types of interconnection schemes are typical in the electronics industry for electrically connecting the components on the board to other components. One scheme uses a special PCB called variously a backplane (active or passive), back panel or motherboard, which connects to the PCB installed into a card cage. The backplane may function as an electronic bridge. In another scheme, the interconnecting bridge may be a wire, a cable or pin connectors. Still a third scheme for connecting components may use both a backplane and interconnecting wiring.
As is well known, card cages and guides are manufactured from many assorted materials, including metals or plastic. In addition, the card guides may be manufactured as separate items, and subsequently attached in some fashion to the card cage. Alternatively, the card guide may be formed from the same material as the card cage and made an integral part of the associated card cage. Further, when metal is the material of choice, the card guides typically take one of three forms: formed or form-up guides, opposing tab guides, or lanced or double bridge lanced card guides. When plastic is the material of manufacture, the guide styles are generally one of the following: snap-in plastic guide, component assembled cage with guide, or fully molded enclosure or card cage.
The field of electronic card guides is crowded, yet none appear to be designed with great adaptability for use in many applications. The design and manufacture of card guides is generally quite complicated, requiring many parts and processes.
In the prior art, many different card guides have been in use for years. Each of the different designs is generally intended for limited applications. As a result, guides which are integral to a card cage often are unable to physically receive all multiple PCB configurations. Another drawback of existing card guides is that as the variety and non-uniform spacing requirements between each PCB has increased, it has become impossible for some card guide designs to be used.
Still another problem with prior art card guides is that in many configurations, specifically, formed metal card guides, the guide forces the edge of the inserted PCB, or multiple PCB configurations, into physical contact with the wall of the card cage. Unfortunately, this situation requires other design considerations, such as: changes to minimize or reduce the associated added heat; modifications to reduce the heat sink flow path; and changes to prevent potential shorting situations. Yet another disadvantage exists with current card guides. As previously described, some PCBs are in multiple board configurations. Because of the large variety of designs of PCBs, manufacturers have chosen to ignore portions of the established industry standards and therefore their designs frequently do not accommodate the various PCB widths that may subsequently be available for inclusion in the card cage.
Methods for manufacturing the card guides have also been unable to provide systems which fully satisfy the needs of the changing technology. For example, previous methods of manufacturing card guides used with electronic systems have been unable to produce a device which is an integral portion of the card cage and which has more than two levels. In addition, other manufacturers have been unable to use computer numerically controlled (CNC) presses to produce parts that are in total compliance with industry established and published specifications. Other manufacturers use methods which sometimes ignore established specifications. Prior methods require multiple parts and multiple steps to create a card guide, thereby incurring higher inventory costs, higher scrap costs, and higher labor costs than the present invention. Prior art manufacturing devices have been designed to push metal in one direction only, which has prevented the production of multiple level card guides of three or more levels in a single tool production system. In contrast, the present invention permits pushing, or forming, the metal part in two directions simultaneously, in a single stroke, thereby reducing the number of steps in the process and concurrently reducing the cost of operation.
Therefore it is clear that a need still exists for a card guide which does provide for separation of the PCB away from the card cage walls; which can accommodate all thicknesses, widths, lengths and configurations of PCBs; which works for all board to board spacings, non-uniform, as well as uniform; works for all interconnecting systems; and complies with industry standards. It would also be an important improvement in the technology to provide a method of manufacturing such a card guide which is simple, fast and relatively inexpensive to use.